[...Well, no point in being coy about everything. It would likely be to his own advantage to be straightforward about some of it while keeping a few other cards a little closer to his chest.]

First of all, Shinji Matou is--or was, at my last recollection--no longer a representative Master from his family. [Not that he ever really was, but that was down to semantics and details that meant nothing. He was inconsequential, and therefore glossed over.] At the time of my most recent memory, the Holy Grail War has been waged for approximately...two weeks, I believe. Illyasviel von Einzbern was in some moderate peril, but still alive.

More pertinent to your question is the matter of a quite literal dark shadow plaguing the war at the moment, and the individual who was until recently influencing it.

Zouken Matou has...or had sway over the vessel of the Lesser Grail.